In an experience no living Washington baseball fan has ever known, the answer to the eternal question “Who’s the starting pitcher tonight?” will be, “Somebody worth watching.”

No, not just on opening day, but for every single game of the season. The Washington Nationals leave spring training with not five or six but seven starting pitchers that are, at the very least, of average major league quality. In more than half the Nats’ games, their starter figures to be a young talent who may someday win 20: Stephen Strasburg, Gio Gonzalez or Jordan Zimmermann.

That’s why the Nationals are entirely different this season — different as entertainment, as consistent competitors in almost every game and different as potential contenders for the playoffs or the National League East division title or, eventually, the World Series. Their rotation makes them brand-new.

If all this makes your head ache with disorientation, you’re entitled to your confusion. Since Nationals Park opened in 2008, no starter has won more than 10 games. And the three of those with 10 wins had losing records. In ’09, only one Nats starter had more than five wins — f-i-v-e. It wasn’t a rotation; it was a swirling toilet bowl. How could you invite friends to watch such a mess?

In the recent past, the Nats’ rotation was prima facie evidence that the team’s management owed its fan base a public apology. That’s now gone.

In baseball, the pitching matchup defines the nature of the game we’ll see more than the identity of the teams themselves. The name on the back of the pitcher’s jersey matters more than the logo of the city that’s on the front.

Proof: In 1972, when Steve Carlton pitched, the Phillies went 29-12, a better winning percentage than that season’s World Series champion. When Carlton didn’t pitch, Philadelphia was 30-85, one of the worst teams ever seen.

Finally, in their big three (plus Edwin Jackson, Ross Detwiler and Chien-Ming Wang when he returns from an injured hamstring) the Nats have names on the back of their uniforms that will make opposing hitters wonder, “Are we really playing the Nats? My batting average aches.”

Double-digit wins are where these guys assume they will start. The towering Wang won 19 games twice as a Yankee. He’s not back there yet. Quite. But he’s closer than 29 teams ever thought he’d be with a dozen pins and screws in his shoulder. The 30th team was the Nats. If GM Mike Rizzo’s two-year wait-and-see pans out, it’ll be one of the season’s best stories.

The four-for-one trade for Gonzalez, 16-12 last year and 15-9 the previous year, demonstrated that the Nats are committed to a winning team right now. In spring training, Gonzalez had baseball’s fourth-best strikeout-per-inning ratio, right behind Roy Halladay. Many Nats fans are in for a surprise. “Gio just has embarrassing stuff,” reliever Drew Storen says.

With their free agent contract to Jackson, the Nats showed that they understood a tricky baseball truth: You never know what year might be your lucky season. That one-year, $11 million deal was an insurance policy. Last year was typical of Jackson’s last four with a 12-9 record, 200 innings, a 3.79 ERA and, for the second time in four years, a starting assignment in the World Series. If this turns into a lucky year, then even after Strasburg is shut down after 160 innings, the Nats are still deep enough to dream.

John Lannan, twice the Nats’ opening day starter, and a durable lefty who may end up with 100 career wins, will be optioned to AAA Syracuse and supplanted by Detwiler, 26, so improved since the middle of last year. A rotation spot for him in 2013 seems likely.

Starting on Thursday, the change from past years is so extreme it’s hard to imagine how we’ll react.

The Nats, 80-81 last year, probably don’t have enough offense yet to be a playoff team. Or maybe they will with the playoffs expanded to five teams in each league; that’s a format where 88 or 89 wins may get you to October.

But with the pitching rotation they have right now, the Nats will win, or lose a close battle, in a large majority of their games. Such one- and two-run games put a premium on defensive range, especially up the middle, and the ability to negate the foe’s running game. The Nats have both talents. Nail-biters also underline the importance of a proven manager. “We’ve lacked an iconic manager,” Jayson Werth said last week. “Now, we have one.”

Most important, in late-inning battles, after the starters are gone, an exceptional bullpen has extra value, particularly a deep one that can, night after night, defend the good work done by the starters, win key game-on-the-line matchups and stay strong even in extra innings.

A fine rotation has a symbiotic relationship with its bullpen. By going deep in games — Gonzalez, Jackson and Wang have had 200-inning seasons and Zimmermann may this year — the bullpen stays rested and sharp. When you need only a couple of relievers to finish a win, not several, then you, in effect, develop an ‘A’ and ‘B’ bullpen. On nights when Tyler Clippard and Storen have closed twice in a row, perhaps Henry Rodriguez and Brad Lidge can finish the job. That flexibility leads to winning streaks.

Nobody said this was a great team, or even in sight of being one. (Yet.) But in baseball’s single most important area — starting pitching — the Nats now have a chance to be one of the better teams. Right now in the NL, they are well behind the Phillies and probably trail the Giants, Diamondbacks, Braves and Brewers, too, though it’s a tightly packed bunch. But the Nats are young — 23, 25, 26, 26, 26, 28 and 32 (Wang). As others get older, they should get better each year. That’s the measure of ’12: How does this rotation evolve?

In particular, will Strasburg become a true ace? Not a Hall of Famer, “just” a real ace? In the five seasons from age 23 through 27, Justin Verlander went 83-50 (before going 24-5 last year at 28). If Strasburg is comparably excellent (an average year of 17-10), he’ll make everybody else better. If he doesn’t, more weight will fall on every other shoulder.

How good are these guys — really?

No one on earth knows. That’s why you get hooked. It’s entirely sane that Strasburg, Gonzalez and Zimmermann, 23, 26 and 25, and all under team control for four to six years, could turned out to be Tim Hudson, Mark Mulder and Barry Zito, who led the Athletics to 100-win seasons.

Or they might rival Tim Lincecum, Matt Cain and Madison Bumgarner, who hurled the Giants to a World Series win two years ago. In Florida, nobody denies this possibility. After all, these aren’t Cooperstown names, just trios of very good pitchers who banded together to do remarkable deeds.

It’s equally undeniable that the Nats could founder — even over a multiyear time frame — like the ’03 Cubs, who had fireballing Mark Prior, Carlos Zambrano and Kerry Wood, ages 22, 22 and 26, plus Matt Clement coming off a 215-strikeout year. Those studs never even got the Cubs a 90-win year.

There’s no such thing as a young rotation with a future that’s sure-fire. If you want ill omens, the Nats’ opener on Thursday is at Wrigley Field.

Starting at 2:20 p.m. that day, and extending for almost six months until closing day on October 3 at Nats Park against the Phillies, Washington will trot out one decent-to-very-good-to-exceptional pitcher almost every single day. By that final afternoon at 1:05 p.m. perhaps nothing at all will be at stake.

Or, just maybe, a great deal could still be on the table for the Nats. If it is the latter, you’ll know why thousands of workers have taken vacation, why school children are sick en masse and why the stands on South Capitol Street are jammed and the concourses packed. And not with Phillies fans.

The core cause of the commotion will be the Nationals’ rotation. Starting this week, because of them, nothing is promised, but all things are possible.

Tom Boswell has been a Washington Post sports columnist since 1984. He started at The Post in 1969 as a copy aide, and he spent 12 years as a general-assignment reporter, covering baseball, golf, college basketball, tennis, boxing and local high school sports.